GaN compound semiconductor light emitting element and method of manufacturing the same

ABSTRACT

The present invention relates to a gallium nitride (GaN) compound semiconductor light emitting element (LED) and a method of manufacturing the same. The present invention provides a vertical GaN LED capable of improving the characteristics of a horizontal LED by means of a metallic protective film layer and a metallic support layer. According to the present invention, a thick metallic protective film layer with a thickness of at least 10 microns is formed on the lateral and/or bottom sides of the vertical GaN LED to protect the element against external impact and to easily separate the chip. Further, a metallic substrate is used instead of a sapphire substrate to efficiently release the generated heat to the outside when the element is operated, so that the LED can be suitable for a high-power application and an element having improved optical output characteristics can also be manufactured. A metallic support layer is formed to protect the element from being distorted or damaged due to impact. Furthermore, a P-type electrode is partially formed on a P-GaN layer in a mesh form to thereby maximize the emission of photons generated in the active layer toward the N-GaN layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/577,710, filed Apr. 20, 2007, which is the National Stage Entry ofInternational Application No. PCT/KR2005/003527, filed Oct. 21, 2005,and claims priority from Korean Patent Application No. 2005-0055348,filed Jun. 25, 2005; Korean Patent Application No. 2004-0098467, filedNov. 29, 2004; and Korean Patent Application No. 2004-0084917, filedOct. 22, 2004, which are hereby incorporated by reference for allpurposes as if fully set forth herein.

TECHNICAL FIELD

The present invention relates to a gallium nitride (GaN) based bluelight emitting diode (LED) and a method of manufacturing the same. Moreparticularly, the present invention relates to a vertical GaN LEDelement and a method of manufacturing the same.

BACKGROUND ART

Recently, the LED using a GaN semiconductor has been predominantlyexpected to replace existing light sources such as incandescent lamps,fluorescent lamps and mercury lamps. Thus, researches on a high-powerGaN LED have been intensively made. In general, a substrate used formanufacturing a GaN LED is configured in such a manner that an n-typeGaN 12, undoped InGaN (an active layer; 14) and a p-type GaN 16 aresequentially grown on a sapphire substrate 10, as shown in FIG. 1. Sincethe sapphire substrate 10 is non-conductive, the LED element typicallyhas a horizontal structure as shown in FIG. 2. Here, reference numerals18, 20, 22 and 24 denote a P-type transparent electrode, a P-type pad,an N-type electrode and an N-type pad, respectively.

In such a case, when it is in a high-power operation, the currentspreading-resistance is high, and thus, its optical output is degraded.In addition, heat generated when the element is operated cannot besmoothly removed and thus thermal stability of the element is degradedto thereby cause a problem related with the high-power operation. Inorder to overcome this problem and implement a high-power GaN LED, aflip-chip LED using a flip-chip packaging method has been proposed andcurrently used. In the case of a flip-chip LED shown in FIG. 3, lightemitted from the active layer 14 is emitted through the sapphiresubstrate 10. Therefore, since a thick p-type ohmic electrode 19 can beused instead of a transparent electrode 18, its currentspreading-resistance can be reduced. Here, reference numerals 25, 30 and32 denotes a solder, a heat sink and a conducting mount, respectively.However, since the flip-chip structure must be packed in the form of aflip-chip, the manufacturing process is complicated. In addition, sincea large amount of light emitted from the active layer 14 is absorbed inthe sapphire while the light is being emitted through the sapphiresubstrate 10, its optical efficiency is also degraded.

DISCLOSURE OF INVENTION Technical Problem

Therefore, the present invention is conceived to solve the aboveproblems. An object of the present invention is to provide a galliumnitride (GaN) compound semi-conductor light emitting element (LED) and amethod of manufacturing the same, in which a multi-layered metallicsupport is formed underside a vertical GaN LED to thereby enable an easychip separation, and an insulation film and metallic protective filmlayer are sequentially formed on a lateral surface of the element tothereby enable the protection of an epitaxially grown GaN substrate.

Another object of the present invention is to provide a GaN compoundsemi-conductor LED and a method of manufacturing the same, in which ap-type reflective film electrode is partially formed on a p-GaN in amesh form and a reflective layer is inserted therebetween such thatphotons formed in an active layer can be maximally emitted toward ann-GaN layer.

A further object of the present invention is to provide a GaN compoundsemi-conductor LED and a method of manufacturing the same, in which ametallic substrate, conductive layer substrate or conductive ceramicsubstrate is used, instead of a sapphire substrate, to efficientlyrelease heat generated upon the operation of the element to the outside,so that the LED can be suitable for a high-power application.

A still further object of the present invention is to provide a GaNcompound semi-conductor LED and a method of manufacturing the same, inwhich photons generated in an InGaN layer are emitted through an n-GaNlayer to provide a short path to the photons, so that the number ofphotons absorbed while being emitted can be reduced.

A still further object of the present invention is to provide a GaNcompound semi-conductor LED and a method of manufacturing the same, inwhich high concentration of doping (>10¹⁹/cm³) into an n-GaN layer canbe obtained to thereby improve electrical conductivity of n-GaN layerand enable to enhance optical output characteristics thereof.

Technical Solution

According to an aspect of the present invention for achieving theobjects, there is provided a light emitting element, comprising ametallic support layer; a P-type reflective film electrode on themetallic support layer; a P-type semiconductor layer, an active layerand an N-type semiconductor layer sequentially formed on the P-typereflective film electrode; and an N-type electrode formed on the N-typesemiconductor layer.

According to another aspect of the present invention, there is provideda light emitting element, comprising a metallic support layer; areflective layer formed on the metallic support layer; a P-typereflective film electrode formed in the form of a mesh on the reflectivelayer; a P-type semiconductor layer, an active layer and an N-typesemiconductor layer sequentially formed on the top of the reflectivelayer including the P-type reflective film electrode; and an N-typeelectrode formed at a desired region on the N-type semiconductor layer.

The light emitting element may further comprise an insulation filmformed at least on a lateral side of the N-type semiconductor layer, anda metallic protective layer for protecting the P-type and N-typesemiconductor layers.

Preferably, the metallic support layer has a multi-layered supportstructure.

The light emitting element may further comprise a protective layerformed on a part of lateral and/or bottom sides of the N-typesemiconductor layer, active layer and P-type semiconductor layer. Thelight emitting element may further comprise an anti-reflective layerthat wraps around the P-type semiconductor layer, active layer andN-type semiconductor layer.

Preferably, the P-type reflective film electrode comprises a contactmetallic layer, a reflective metallic layer, a diffusion barrier layerand a bonding metallic layer. At this time, the contact metallic layeris formed of at least one of Ni, Ir, Pt, Pd, Au, Ti, Ru, W, Ta, V, Co,Os, Re and Rh. The reflective metallic layer is formed of Al or Ag. Thediffusion barrier layer is formed of at least one of Ru, Ir, Re, Rh, Os,V, Ta, W, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), RuO₂, VO₂,MgO, IrO₂, ReO₂, RhO₂, OsO₂, Ta₂O₃ and WO₂. The bonding metallic layeris composed of first and second bonding metallic layers. The firstbonding metallic layer is formed of at least one of Ni, Cr, Ti, Pd, Ru,Ir, Rh, Re, Os, V and Ta. The second bonding metallic layer is formed ofat least one of Au, Pd and Pt.

According to a further aspect of the present invention, there isprovided a light emitting element, comprising a P-type semiconductorlayer; an active layer and an N-type semiconductor layer formed on theP-type semiconductor layer; an N-type electrode formed on the N-typesemiconductor layer; an insulation film formed on at least a lateralside of the N-type semiconductor layer; and a metallic protective layerfor protecting the P-type semiconductor layer and N-type semiconductorlayer.

Preferably, the metallic protective layer is formed on lateral sides ofthe P-type and N-type semiconductor layers and on a bottom side of theP-type semiconductor layer.

In addition, the light emitting element may further comprise aninsulation layer formed on a part of a bottom side of the P-typesemiconductor layer. Preferably, the insulation layer extends to alateral side of the active layer.

The light emitting element may further comprise an anti-reflective layerformed on the N-type semiconductor layer.

Of course, the light emitting element may further comprise a P-typeelectrode formed beneath the P-type semiconductor layer. Preferably, theP-type electrode includes a contact metallic layer, a reflectivemetallic layer, a diffusion barrier layer and a bonding metallic layer.At this time, the contact metallic layer is formed of at least one ofNi, Ir, Pt, Pd, Au, Ti, Ru, W, Ta, V, Co, Os, Re and Rh. The reflectivemetallic layer is formed of Al or Ag. The diffusion barrier layer isformed of at least one of Ru, Ir, Re, Rh, Os, V, Ta, W, ITO (Indium TinOxide), IZO (Indium Zinc Oxide), RuO₂, VO₂, MgO, IrO₂, ReO₂, RhO₂, OsO₂,Ta₂O₃ and WO₂. The bonding metallic layer is composed of first andsecond bonding metallic layers. The first bonding metallic layer isformed of at least one of Ni, Cr, Ti, Pd, Ru, Ir, Rh, Re, Os, V and Ta.The second bonding metallic layer is formed of at least one of Au, Pdand Pt.

According to a still further aspect of the present invention forachieving the objects, there is provided a method of manufacturing alight emitting element, comprising the steps of sequentially forming anN-type semiconductor layer, an active layer and a P-type semiconductorlayer on a substrate; isolating the element by partially etching theP-type semiconductor layer, the active layer, the N-type semiconductorlayer and the substrate; forming a P-type reflective film electrode onthe isolated P-type semi-conductor layer and forming a first metallicsupport layer on the whole structure; removing the substrate; andforming an N-type electrode on the N-type semiconductor layer.

According to a still further aspect of the present invention, there isprovided a method of manufacturing a light emitting element, comprisingthe steps of sequentially forming an N-type semiconductor layer, anactive layer, a P-type semiconductor layer, a P-type reflective filmelectrode and a first metallic support layer on a substrate; removingthe substrate; isolating the element by partially etching the P-typesemi-conductor layer, the active layer and the N-type semiconductorlayer; and forming an N-type electrode on the N-type semiconductorlayer.

Preferably, an isolated second metallic support layer is formed on thefirst metallic support layer, and the first and second metallic supportlayers are formed through an electro-plating method or using a vacuumvapor-deposition apparatus such as a thermal evaporator, an e-beamevaporator, a laser evaporator, a sputter and an MOCVD apparatus.

More preferably, the first and second metallic support layers are formedof at least one of Au, Ni, W, Mo, Cu, Al, Ta, Ag, Pt and Cr, or using aconductive ceramic substrate such as SrTiO₃ doped with Nb, ZnO dopedwith Al, ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) or asemiconductor substrate such as B-doped Si, As-doped Si and diamonddoped with impurities, and a total thickness of the first and secondmetallic support layers is 0.5 to 200 nm.

The method of manufacturing a light emitting element may furthercomprise the step of, after the step of isolating the element, forming aprotective layer for protecting the isolated P-type semiconductor layer,active layer and N-type semiconductor layer. In addition, the method ofmanufacturing a light emitting element may further comprise the step of,after the step of isolating the element, forming an anti-reflectivelayer wrapping around the isolated P-type semiconductor layer, activelayer and N-type semiconductor layer.

Preferably, a portion of the anti-reflective layer formed on the N-typesemi-conductor layer is removed and the N-type electrode is then formedon the removed portion of the anti-reflective layer.

According to a still further aspect of the present invention, there isprovided a method of manufacturing a vertical semiconductor lightemitting element, comprising the steps of sequentially forming an N-typesemiconductor layer, an active layer and a P-type semiconductor layer ona substrate; forming an insulation film on a lateral side of the N-typesemiconductor layer except a portion of the P-type semiconductor layer;forming a P-type electrode on the portion of the P-type semiconductorlayer on which the insulation film is not formed; forming a metallicsupport film layer in such a way to wrap around the P-type and N-typesemiconductor layers; removing the substrate; and forming an N-typeelectrode on the N-type semiconductor layer.

Here, the method of manufacturing a vertical semiconductor lightemitting element may further comprise the step of, after the step offorming the P-type electrode, forming a reflective layer on the P-typesemiconductor layer on which the P-type electrode is formed.

The method of manufacturing a vertical semiconductor light emittingelement may further comprise the steps of, after the step of forming areflective layer on the P-type semiconductor layer, removing thereflective layer on a region on which the P-type electrode will beformed and forming the P-type electrode on the region from which thereflective layer is removed.

The method of manufacturing a vertical semiconductor light emittingelement may further comprise the step of, after the step of forming themetallic protective film layer, forming a metallic support layer on theP-type semiconductor layer on which the metallic protective film layeris formed.

The method of manufacturing a vertical semiconductor light emittingelement may further comprise the steps of, after the step of removingthe substrate, forming an anti-reflective layer on the N-typesemiconductor layer and exposing a portion of the N-type semiconductorlayer by removing a portion of the anti-reflective layer.

Preferably, the step of forming the insulation film on a lateral side ofthe N-type semiconductor layer except a portion of the P-typesemiconductor layer comprises the steps of forming the insulation filmin such a way to wrap around the P-type and N-type semiconductor layersand removing the portion of the insulation film from the P-typesemiconductor layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a thin film structure of a conventional GaN-based blue LEDsubstrate.

FIG. 2 is a sectional view of a horizontal LED.

FIG. 3 is a sectional view of a flip-chip LED.

FIGS. 4 to 7 are sectional views of a vertical LED according to a firstembodiment of the present invention.

FIGS. 8 to 15 show a process of manufacturing the vertical LED elementaccording to the first embodiment of the present invention.

FIGS. 16 to 45 show a process of manufacturing a vertical LED elementaccording to modified embodiments of the present invention.

FIG. 46 is a plan view illustrating an n-type electrode structure.

FIG. 47 is an SEM photograph of the LED element according to the presentinvention.

FIGS. 48 and 49 are graphs plotting comparison results of electrical andoptical characteristics of the vertical LED element manufacturedaccording to the first embodiment of the present invention and aconventional horizontal LED element.

FIG. 50 is a graph plotting comparison results of optical outputcharacteristics with respect to an injection current in a conventionalhorizontal LED and a vertical LED of the present invention.

FIGS. 51 and 52 are graphs plotting comparison results of electrical andoptical characteristics of the vertical LED elements manufactured by theprocess illustrated in FIGS. 30 to 33 and 8 to 15.

FIGS. 53 to 58 are sectional views of a vertical LED according to asecond embodiment of the present invention.

FIGS. 59 to 66 are a series of sectional views illustrating a process ofmanufacturing the vertical LED element according to the secondembodiment of the present invention.

FIGS. 67 to 90 are a series of sectional views illustrating a process ofmanufacturing a vertical LED element according to a modified embodimentof the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. However, the presentinvention is not limited to the embodiments set forth herein, but willbe implemented in many different forms. Rather, the embodiments of thepresent invention are provided such that the disclosure will becompleted and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, like reference numerals denote likeelements.

FIG. 4 is a sectional view of a vertical LED according to a firstembodiment of the present invention, and FIGS. 5 to 7 are sectionalviews of a vertical LED according to a modified embodiment of thepresent invention.

As shown in FIG. 4, the vertical GaN LED of this embodiment includes ametallic support layer 100, a reflective film electrode 110 (a p-typereflective film ohmic electrode layer), a p-type semiconductor layer120, an InGaN active layer 130 and an n-type semiconductor layer 140 insequence from the bottom.

Referring to FIG. 5, a vertical GaN LED according to a modifiedembodiment of the present invention employs a double-layered metallicsupport composed of first and second metallic support layer 101 and 102to enable easy chip separation. In a vertical GaN LED shown in FIG. 6, ap-type reflective film electrode 110 is partially formed on a p-typesemiconductor in a mesh form and a reflective layer 103 is then insertedtherebetween, so that light generated in the i-InGaN (the active layer130) can be maximally emitted toward the n-type semiconductor layer 140.Comparing with the vertical GaN LED shown in FIG. 6, a vertical GaN LEDshown in FIG. 7 employs a double-layered metallic support 101 and 102,thereby enabling the easy chip separation. Here, reference numerals 150,160 and 162 denote an n-type ohmic electrode, an anti-reflective layerand a protective layer, respectively.

Hereinafter, a method of manufacturing the vertical LED element soconfigured will be explained with reference to the accompanyingdrawings.

FIGS. 8 to 15 are a series of sectional views illustrating a process ofmanufacturing a vertical LED element according to the first embodimentof the present invention.

FIG. 8 is a sectional view of a common GaN LED substrate. An n-typesemi-conductor layer 140, an InGaN active layer 130 and a p-typesemiconductor layer 120 are grown sequentially on a sapphire substrate200. The total thickness of the thin film is approximately 4 microns,and the thin film is deposited through a metal-organic chemical vapordeposition (MOCVD).

FIG. 9 shows a process of etching an area other than the element region.The etching process is performed through a dry-etching method in a statewhere Cl₂ gas flows after a substrate has been masked using photoresistor SiO₂. FIG. 10 shows a process of forming a p-type reflective filmohmic electrode 110. On the substrate etched for the element isolationis formed a SiO₂ protective layer 162 with a thickness of 0.05˜5.0microns through a plasma-enhanced chemical vapor deposition (PECVD). Inorder to form a reflective film ohmic electrode 110, a micro pattern isformed and an etching is then performed using buffered oxide etchant(BOE) or CF₄ gas through a dry-etching method and using a photoresist asa mask. Thereafter, a metallic ohmic layer is deposited. Typically, Niand Au are deposited with a thickness of several tens to severalhundreds of nanometers using an e-beam evaporator. However, sincereflectivity is important in case of a vertical LED shown in FIGS. 4 to7, metals including Ni/Ag, Pt/Ag, Ru/Ag, Ir/Ag or the like are used.Then, heat treatment is performed within a temperature range of 300 to600° C. to form the reflective film ohmic electrode 110.

FIG. 11 shows a process of forming a metallic support layer 100 with athickness of several microns to several tens of microns and radiating alaser. The metallic support layer 100 is formed through anelectro-plating method, a vacuum vapor-deposition method such assputtering, e-beam evaporation or thermal evaporation, or a waferdiffusion bonding method in which a metallic substrate is placed on ap-type electrode and they are pressed under a certain pressure at around300° C. such that they are bonded to each other. When a laser isradiated through sapphire, the laser is absorbed in the GaN layer whichin turn is decomposed into a Ga metal and N₂ gas. At this time, themetallic support layer 100 serves to prevent the GaN thin film layerwith a thickness of about 4 microns from being destroyed when thesapphire substrate 200 is removed by means of the laser radiation.

FIG. 12 shows a state where a GaN thin film layer is attached to themetallic support layer 100 after the sapphire substrate 200 has beenremoved. FIG. 13 is a sectional view showing a state where ananti-reflective layer 160 is coated on the n-type semi-conductor layer140 such that photons generated in the i-InGaN active layer 130 can besmoothly emitted to the outside of the substrate. The anti-reflectivelayer 160 is formed of SiO₂ or Si₃N₄ which is deposited through thePECVD method.

FIG. 14 is a sectional view illustrating a state after portions of theanti-reflective layer 160 have been etched and an n-type ohmic electrode150 is then formed on the etched portions. The N-type ohmic electrode isformed of Ti/Al or Cr/Au, or Ti/Al or Cr/Au on which Cr/Au or Ni/Au isdeposited using an e-beam evaporator. FIG. 15 is a sectional viewshowing a state after the chip has been separated. The chip is separatedthrough a dicing or laser-cutting technique.

FIGS. 16 to 45 show a series of processes of manufacturing a verticalLED element according to a modified embodiment of the present invention.

Referring to FIG. 16, a sapphire substrate 200 on which desired GaNlayers are formed is first prepared in a similar manner to FIG. 8. Next,before performing a trench etching process, a p-type reflective filmohmic electrode 110 and a metallic support layer 100 are formed (FIGS.17 and 18) and a laser is then radiated to remove the sapphire substrate200 (FIG. 19). The substrate (n-GaN, I-InGaN, p-GaN) is etched toisolate the elements from each other (FIG. 20). After coating ananti-reflective layer 160 (FIG. 21), an n-type electrode 150 is formed(FIG. 22) and the chip is separated (FIG. 23) to complete a vertical LEDstructure.

Next, a process of manufacturing a vertical LED element of the modifiedembodiment will be explained with reference to FIGS. 24 to 26. Here,FIGS. 24 to 26 show processing steps of manufacturing the vertical LEDshown in FIG. 7. A substrate that has been explained in conjunction withFIGS. 8 to 11 is first prepared. That is, a substrate with a firstmetallic support layer 102 formed thereon is prepared. A pattern isformed on an area corresponding to the chip using a photoresist film anda second metallic support layer 101 is then formed using the photoresistas a mask (FIG. 24). A laser is radiated to remove the sapphiresubstrate 200 (FIG. 25). That is, a step of FIG. 12 and its subsequentprocess are performed to obtain the vertical LED having theconfiguration shown in FIG. 5.

More specifically, FIG. 25 shows a step of radiating a laser to removethe substrate as shown in FIG. 11 and forming a pattern on an areacorresponding to the chip using a photoresist as shown in FIG. 12 andthen forming a second metallic support layer 101 using the photoresistas a mask. Subsequently, a laser is radiated for removing the sapphiresubstrate 200. The subsequent processes are the same as those subsequentto FIG. 12. Since a double-layered metallic support is employed, abreaking process can be easily performed as shown in FIG. 26. Thus,there is an advantage in that the chip can be easily separated.Consequently, a vertical LED having the structure shown in FIG. 5 can beobtained.

Next, a process of manufacturing a vertical LED element of this modifiedembodiment will be explained with reference to FIGS. 27 to 29. Here,FIGS. 27 to 29 are a sectional views illustrating processing steps ofmanufacturing a vertical LED shown in FIG. 5.

FIG. 27 is a sectional view showing a state after the processes of FIGS.16 to 19 are performed, a second metallic support layer 101 is furtherformed, and the sapphire substrate is then removed using a laser. Morespecifically, the vertical LED having the structure shown in FIG. 5 isobtained by performing the process of FIG. 19 and its subsequentprocesses.

FIG. 28 is a sectional view showing a state the substrate is then etchedfor the element isolation as shown in FIG. 20. The subsequent processesare the same as those after FIG. 21. Since a double-layered metallicsupport is employed, a breaking process can be easily performed as shownin FIG. 29. Thus, there is an advantage in that the chip can be easilyseparated. Consequently, a vertical LED having the structure shown inFIG. 5 can be obtained.

Next, a process of manufacturing a vertical LED element of this modifiedembodiment will be explained with reference to FIGS. 30 to 33. Here,FIGS. 30 to 33 are sectional views illustrating processing steps ofmanufacturing a vertical LED of FIG. 6.

As shown in FIG. 30, after the processes up to FIG. 9 have beenfinished, a SiO₂ protective film 162 with a thickness of 0.05˜5.0microns is vapor-deposited over the whole surface using a PECVD method.Then, a micro-pattern is formed in a mesh form. Using a photoresist as amask, the SiO₂ protective film 162 is dry-etched using the BOE or CF₄gas. A p-type ohmic metal is deposited on portions with the SiO₂ removedtherefrom, and a p-type reflective film ohmic electrode 110 is thenformed through the heat treatment.

Here, Ni and Au may be deposited with a thickness of several tens toseveral hundreds of nanometers using an e-beam evaporator. However,since reflectivity is important in case of a vertical LED shown in FIGS.4 to 7, metals including Ni/Ag, Pt/Ag, Ru/Ag, Ir/Ag or the like areused. Then, the rapid thermal annealing is performed for several secondsto several minutes at a temperature of 300 to 600° C. to form theelectrode.

Thereafter, as shown in FIG. 31, Ag or Al-based reflective film 103 isdeposited on the p-type reflective ohmic electrode in the form of amesh. FIG. 32 shows a process of forming a metallic support layer 100with a thickness of several microns to several tens of microns andradiating a laser. The metallic support layer 100 is formed through anelectroplating method, a vacuum vapor-deposition method such assputtering, e-beam evaporation or thermal evaporation, or a waferdiffusion bonding method in which a metallic substrate is placed on ap-type electrode and they are pressed under a certain pressure at around300° C. such that they are bonded to each other. When a laser isradiated through sapphire, the laser is absorbed in the GaN layer whichin turn is decomposed into a Ga metal and N₂ gas. At this time, themetallic support layer 100 serves to prevent the GaN thin film layerwith a thickness of about 4 microns from being destroyed when thesapphire substrate 200 is removed by means of the laser radiation. Thesubsequent processes are the same as those shown in FIGS. 12 to 14. FIG.33 shows a sectional view after the chip has been separated.

Hereinafter, a process of manufacturing a vertical LED element of thismodified embodiment will be explained with reference to FIGS. 34 to 37.Here, FIGS. 34 to 37 are sectional views illustrating processing stepsof manufacturing a vertical LED of FIG. 6.

Referring to FIG. 34, a SiO₂ protective film 162 with a thickness of0.05˜5.0 microns is vapor-deposited on a desired substrate shown in FIG.16 using a PECVD method.

As shown in FIG. 35, a micro-pattern is formed in a mesh form. Using aphotoresist as a mask, the SiO₂ protective film 162 is dry-etched usingthe BOE or CF₄ gas. A p-type reflective film ohmic metal is deposited onportions with the SiO₂ removed therefrom, and a p-type reflective filmohmic electrode 110 is then formed through the heat treatment. Ni and Aumay be deposited with a thickness of several tens to several hundreds ofnanometers using an e-beam evaporator. However, since reflectivity isimportant in case of a vertical LED shown in FIGS. 4 to 7, metalsincluding Ni/Ag, Pt/Ag, Ru/Ag, Ir/Ag or the like are used. Then, therapid thermal annealing is performed for several seconds to severalminutes at a temperature of 300 to 600° C. to form the electrode.Thereafter, Ag or Al-based reflective film 103 is deposited on thep-type reflective ohmic electrode 110.

FIG. 36 shows a process of forming a metallic support layer 100 with athickness of several microns to several tens of microns and radiating alaser. The metallic support layer 100 is formed through anelectro-plating method, a vacuum vapor-deposition method such assputtering, e-beam evaporation or thermal evaporation, or a waferdiffusion bonding method in which a metallic substrate is placed on ap-type electrode and they are pressed under a certain pressure at around300° C. such that they are bonded to each other. When a laser isradiated through sapphire, the laser is absorbed in the GaN layer whichin turn is decomposed into a Ga metal and N₂ gas. At this time, themetallic support layer 100 serves to prevent the GaN thin film layerwith a thickness of about 4 microns from being destroyed when thesapphire substrate 200 is removed by means of the laser radiation. Thesubsequent processes are the same as those shown in FIGS. 20, 21 and 22.FIG. 37 shows a sectional view after the chip has been separated.

Next, a process of manufacturing a vertical LED element of this modifiedembodiment will be explained with reference to FIGS. 38 to 41. FIGS. 38to 41 are sectional views illustrating processing steps of manufacturinga vertical LED of FIG. 7.

As shown in FIG. 38, after the process of FIG. 9 has been finished, aSiO₂ protective film 162 with a thickness of 0.05˜5.0 microns isvapor-deposited over the whole surface using a PECVD method. Then, amicro-pattern is formed in a mesh form. Using a photoresist as a mask,the SiO₂ protective film 162 is dry-etched using the BOE or CF₄ gas. Ap-type ohmic metal is deposited on portions with the SiO₂ removedtherefrom, and a p-type reflective film ohmic electrode 110 is thenformed through the heat treatment.

Here, Ni and Au may be deposited with a thickness of several tens toseveral hundreds of nanometers using an e-beam evaporator. However,since reflectivity is important in case of a vertical LED shown in FIGS.4 to 7, metals including Ni/Ag, Pt/Ag, Ru/Ag, Ir/Ag or the like areused. Then, the rapid thermal annealing is performed for several secondsto several minutes at a temperature of 300 to 600° C. to form theelectrode.

As shown in FIG. 39, Ag or Al-based reflective film is deposited on thep-type reflective ohmic electrode 110 in the form of a mesh. Then, asshown in FIG. 40, a first metallic support layer 102 is formed at athickness of several microns to several tens of microns. A pattern isformed on an area corresponding to the chip using a photoresist film anda second metallic support layer 101 is then formed. Thereafter, a laseris radiated to remove the sapphire substrate 200. The first metallicsupport layer 102 is formed through an electroplating method, a vacuumvapor-deposition method such as sputtering, e-beam evaporation orthermal evaporation, or a wafer diffusion bonding method in which ametallic substrate is placed on a p-type electrode and they are pressedunder a certain pressure at around 300° C. such that they are bonded toeach other. The second metallic support layer 101 is formed through anelectroplating method, or a vacuum vapor-deposition method such assputtering, e-beam evaporation or thermal evaporation. When a laser isradiated through sapphire, the laser is absorbed in the GaN layer whichin turn is decomposed into a Ga metal and N₂ gas. At this time, themetallic support layer serves to prevent the GaN thin film layer with athickness of about 4 microns from being destroyed when the sapphiresubstrate 200 is removed by means of the laser radiation. The subsequentprocesses are the same as those shown in FIGS. 12, 13 and 14. FIG. 41shows a sectional view after the chip has been separated.

Next, a process of manufacturing a vertical LED element of this modifiedembodiment will be explained with reference to FIGS. 42 to 45. Here,FIGS. 42 to 45 are sectional views showing processing steps ofmanufacturing a vertical LED of FIG. 7.

Referring to FIG. 42, a SiO₂ protective film 162 with a thickness of0.05˜5.0 microns is vapor-deposited on a desired substrate of FIG. 16using a PECVD method. Then, a micro-pattern is formed in a mesh form.Using a photoresist as a mask, the SiO₂ protective film 162 isdry-etched using the BOE or CF₂ gas. A p-type reflective film ohmicmetal is deposited on portions with the SiO₂ removed therefrom, and ap-type reflective film ohmic electrode 110 is then formed through theheat treatment. Generally, Ni and Au may be deposited with a thicknessof several tens to several hundreds of nanometers using an e-beamevaporator. However, since reflectivity is important in case of avertical LED shown in FIGS. 4 to 7, metals including Ni/Ag, Pt/Ag,Ru/Ag, Ir/Ag or the like are used. Then, the rapid thermal annealing isperformed for several seconds to several minutes at a temperature of 300to 600° C. to form the electrode. Thereafter, Ag or Al-based reflectivefilm 103 is deposited on the p-type reflective ohmic electrode 110.

As shown in FIG. 43, a first metallic support layer 102 is formed at athickness of several microns to several tens of microns. A pattern isformed on an area corresponding to the chip using a photoresist film anda second metallic support layer 101 is then formed. Thereafter, a laseris radiated to remove the sapphire substrate 200. The first metallicsupport layer 102 is formed through an electroplating method, a vacuumvapor-deposition method such as sputtering, e-beam evaporation orthermal evaporation, or a wafer diffusion bonding method in which ametallic substrate is placed on a p-type electrode and they are pressedunder a certain pressure at around 300° C. such that they are bonded toeach other. The second metallic support layer 101 is formed through anelectroplating method, or a vacuum vapor-deposition method such assputtering, e-beam evaporation or thermal evaporation. When a laser isradiated through sapphire, the laser is absorbed in the GaN layer whichin turn is decomposed into a Ga metal and N₂ gas. At this time, themetallic support layer serves to prevent the GaN thin film layer with athickness of about 4 microns from being destroyed when the sapphiresubstrate 200 is removed by means of the laser radiation.

FIG. 44 shows a sectional view after the sapphire substrate 200 has beenremoved.

The subsequent processes are the same as those shown in FIGS. 20, 21 and22. FIG. 45 shows a sectional view after the chip has been separated.

The vertical LED element of the present invention may be manufacturedthrough a variety of processes of manufacturing a semiconductor devicein addition to the above described process. That is, the respectivelayers may be formed through various other deposition processes. Theetching process may be performed using a wet- or dry-etching method.Further, the patterning process may use a barrier film instead of thephotoresist film.

FIG. 46 is a plan view illustrating an n-type electrode structure.

As shown in FIG. 46, if an X-shaped branch is installed around an n-typeelectrode pad, the diffusion resistance of current can be reduced.Therefore, since electrons can be uniformly injected, optical output canbe improved. Of course, the present invention is not limited thereto,but a variety of shapes of N-type electrodes can be employed to improvethe optical output.

FIG. 47 is an SEM photograph of the LED element according to the presentinvention.

More specifically, FIG. 47 is an SEM photograph showing a two-inchsubstrate, from which the sapphire is removed through the processillustrated in FIGS. 8 to 15 according to the present invention, and LEDelements arranged on the substrate, using a scanning electronmicroscope. It can be seen from FIG. 47 that the sapphire has beencompletely removed from the two-inch substrate and all the elementsformed therein are kept at a good state.

FIGS. 48 and 49 are graphs plotting comparison results of electrical andoptical characteristics of the vertical LED element manufacturedaccording to the first embodiment of the present invention and theconventional horizontal LED element.

FIG. 48 is a graph plotting comparison results of current-voltagecharacteristics of the horizontal and vertical LED elements. It has beenfound that, when the injection current is 20 mA, the forward voltage ofthe vertical LED is 3.3 V which is lower by 0.2 V than 3.5 V of thehorizontal LED. Thus, it indicates that the vertical LED has lower powerconsumption than the horizontal LED. FIG. 49 shows comparison results ofthe optical output characteristics of the horizontal and vertical LEDelements, which indicates that the latter has the optical outputcharacteristics at least 2.5 times greater than the former. This meansthat the vertical LED emits light 2.5 times brighter than that of thehorizontal LED at the same power consumption level.

FIG. 50 is a graph plotting comparison results of optical outputcharacteristics with respect to an injection current in the conventionalhorizontal LED and the vertical LED of the present invention.

That is, the optical output characteristics with respect to theinjection current are examined for the horizontal LED of FIG. 2 and thevertical LED of FIG. 4 manufactured through the process of FIGS. 8 to15. It can be seen from FIG. 50 that the vertical LED emits light about2.5 times brighter than that of the horizontal LED.

FIGS. 51 and 52 are graphs plotting comparison results of electrical andoptical characteristics of the vertical LED elements manufactured by theprocess illustrated in FIGS. 30 to 33.

Here, an Ag film obtained by thermally depositing pure Ag of above 99%at a thickness of 500 nm has been used as a reflective film. FIG. 51 isa graph plotting comparison results of the current-voltagecharacteristics of the vertical LED elements manufactured through theprocesses of FIGS. 30 to 33 and FIGS. 8 to 15 according to the presentinvention. When the injection current is 20 mA, the forward voltages ofboth elements are 3.3 V. FIG. 52 is a graph plotting comparison resultsof optical output characteristics of the vertical LED elementsmanufactured through the processes of FIGS. 30 to 33 and FIGS. 8 to 15according to the present invention. It can be seen from FIG. 52 that theoptical output characteristics have been improved by at least 20%. Thisis because the Ag-film has a reflectivity of at least 98%. That is, ithas been confirmed that the optical characteristic of the vertical LEDelement can be improved by at least 20% through the process illustratedin FIGS. 30 to 33.

The present invention is not limited to the foregoing. For example, theepitaxially grown GaN substrate can be protected by forming aninsulation film on a lateral surface of the element and then coating ametallic protective film layer on a top surface of the P-type electrodeand the lateral surface of the element. Hereinafter, a vertical LEDhaving a metallic protective film layer according to a second embodimentof the present invention will be described.

FIG. 53 is a sectional view of a vertical LED according to the secondembodiment of the present invention. FIGS. 54 to 58 are sectional viewsof a vertical LED according to modified embodiments of the presentinvention.

Referring to FIG. 53, the vertical GaN LED is configured in such amanner that an insulation film 1700 is first coated on the lateralsurface of the element composed of a P-type semiconductor layer 1300, anactive layer 1400 and an N-type semiconductor layer 1500, and a metallicprotective film layer 1100 is then coated on a bottom surface of aP-type electrode 1200 and a lateral face of the insulation layer toprotect an epitaxially grown GaN substrate with a thickness of merely4˜5 microns. That is, the thick metallic protective film layer 1100 witha thickness of 10 microns or more is provided on the bottom and lateralsurfaces of the element, and then, the P-type electrode 1200, P-typesemiconductor layer 1300, active layer 1400, N-type semi-conductor layer1500 and N-type electrode 1600 are sequentially provided on the metallicprotective film layer. As shown in FIG. 54, a second vertical GaN LEDstructure according to a modified example of the second embodiment isbased on the first structure of the second embodiment according to thepresent invention, but different in that an anti-reflective coating 1800is provided on the light-emitting N-type semiconductor layer to therebyimprove the optical characteristics and durability of the vertical GaNLED. As shown in FIG. 55, a third structure is also based on the firststructure but is different in that a thick metallic support layer 1900is coated beneath the metallic protective film layer 1100 to enable easychip separation. At this time, the underlying metallic support layer1900 serves as bridge posts between which an empty space is provided.Therefore, the chip can be easily separated since the metallic supportlayer 1900 has a structure in which a pressing force can be mechanicallyapplied to a position between the two bridge posts.

As illustrated in FIG. 56, a fourth vertical GaN LED structure is alsobased on the first structure, but is different in that P-type electrodes1200 are partially formed on the P-type semiconductor layer in the formof a mesh and a reflective layer 2000 is then inserted between thepartially formed electrodes to thereby maximize the emission of photonsgenerated from the active layer 1400 toward the N-type semiconductorlayer 1500. As shown in FIG. 57, a fifth vertical GaN LED structure isbased on the aforementioned fourth structure, but is different in thatan anti-reflective coating is further provided on the light-emittingN-type semiconductor layer 1500 to thereby improve the opticalcharacteristics and durability of the vertical GaN LED. As shown in FIG.58, a sixth vertical GaN LED structure is also based on the fifthstructure, but is different in that a thick metallic support layer 1900is coated beneath the metallic protective film layer 1100 to therebyenable the easy chip separation.

Referring to FIG. 53 to FIG. 58, the vertical GaN LED comprises theP-type semi-conductor layer 1300, the active layer 1400 and N-typesemiconductor layer 1500 formed on the P-type semiconductor layer, theN-type electrode 1600 formed on the N-type semiconductor layer 1500, andthe metallic protective film layer 1100 for protecting the P-typesemiconductor layer 1300, active layer 1400 and N-type semi-conductorlayer 1500. Here, the metallic protective film layer 1100 is formed onthe lateral sides of the P-type semiconductor layer 1300, active layer1400 and N-type semiconductor layer 1500, and below the P-typesemiconductor layer 1300. In addition, the P-type electrode 1200 isfurther provided between the metallic protective film layer 1100 and theP-type semiconductor layer 1300. Preferably, the P-type electrode 1200is formed in a mesh form. Further, the insulation film 1700 is furtherprovided between the metallic protective film layer 1100 and the lateralsides of the N-type semiconductor layer 1500, active layer 1400 andP-type semiconductor layer 1300. Furthermore, the reflective layer 2000may be further formed between the P-type semiconductor layer 1300 andthe metallic protective film layer 1100. The metallic support layer 1900may be further formed beneath the metallic protective film layer 1100.

The vertical GaN LED of this embodiment shown in FIG. 53 comprises theP-type electrode 1200, the P-type semiconductor layer 1300, the activelayer 1400, the N-type semiconductor layer 1500 and the N-type electrode1600, which are sequentially formed. The insulation film 1700 is formedto protect the lateral sides of the P-type semiconductor layer 1300,active layer 1400 and N-type semiconductor layer 1500. The metallicprotective film layer 1100 is also formed around the insulation film1700 and P-type electrode 1200. At this time, the insulation film 1700may be formed only on the lateral side of the N-type semiconductor layer1500 or on the lateral side of the P-type semiconductor layer 1300. Asshown in FIG. 54, the vertical GaN LED of this modified example isprovided with the anti-reflective layer 1800 formed on the N-typesemiconductor layer 1500 of the vertical GaN LED shown in FIG. 53,thereby providing an advantageous effect of inhibiting light reflection.The vertical GaN LED of FIG. 55 is provided with the metallic supportlayer 1900 formed beneath the metallic protective film layer 1100 of thevertical GaN LED shown in FIG. 54. The vertical GaN LED of FIG. 56comprises the reflective layer 2000; the P-type electrode 1200 formed onthe reflective layer 2000 in a mesh form; the P-type semiconductor layer1300, active layer 1400, N-type semiconductor layer 1500 and N-typeelectrode 1600 which are sequentially formed on the P-type electrode1200; the insulation film 1700 formed on the lateral sides of the P-typesemiconductor layer 1300, active layer 1400 and N-type semiconductorlayer 1500; and the metallic protective film layer 1100 formed to wraparound the insulation film 1700 and reflective layer 2000. Here, asshown in the figure, the insulation film 1700 may be partially formed onthe bottom surface of the P-type semiconductor layer 1300. The verticalGaN LED of FIG. 57 is provided with the anti-reflective layer 1800formed on the N-type semiconductor layer 1500 of the vertical LED shownin FIG. 56. The vertical LED of FIG. 58 is provided with the metallicsupport layer 1900 formed beneath the metallic protective film layer1100 of the vertical LED illustrated in FIG. 57.

Preferably, an ohmic electrode layer with good thermal stability and ahigh reflectivity of at least 90% is used as the P-type electrode 1200formed on the underside of the P-type semiconductor layer 1300. Thisohmic electrode layer, i.e. the P-type electrode 1200, includes acontact metallic layer 1210, a reflective metallic layer 1220, adiffusion barrier layer 1230 and bonding metallic layers 1240 and 1250.The whole thickness of the P-type electrode 1200 is 300˜23000 Å,preferably 2000˜5000 Å.

Here, the contact metallic layer 1210 has a thickness of 5˜500 Å,preferably no more than 200 Å. The thickness of the contact metalliclayer 1210 is restricted to the above range to control the amount oflight absorption. In addition, the contact metallic layer 1210 may beformed in a multi-layered thin film. The contact metallic layer 1210 isformed of at least one of Ni, Ir, Pt, Pd, Au, Ti, Ru, W, Ta, V, Co, Os,Re and Rh, preferably of a laminated metal of Ni, Ir and Pt.

The reflective metallic layer 1220 has a thickness of 100˜9000 Å,preferably 1000˜2000 Å. The reflective metallic layer 1220 is formed ofAl and/or Ag, preferably of Ag.

The diffusion barrier layer 1230 has a thickness of 50˜1000 Å,preferably 100˜800 Å. The diffusion barrier layer 1230 is formed of atleast one of Ru, Ir, Re, Rh, Os, V, Ta, W, ITO (Indium Tin Oxide), IZO(Indium Zinc Oxide), RuO₂, VO₂, MgO, IrO₂, ReO₂, RhO₂, OsO₂, Ta₂O₃ andWO₂, preferably of Ru.

The bonding metallic layers are composed of first and second bondingmetallic layers 1240 and 1250. The first bonding metallic layer 1240 hasa thickness of 100˜3000 Å, preferably no more than 1000 Å. The firstbonding metallic layer 1240 is formed of at least one of Ni, Cr, Ti, Pd,Ru, Ir, Rh, Re, Os, V and Ta, preferably of Ni.

The second bonding metallic layer 1250 has a thickness of 100˜9000 Å,preferably no more than 1000 Å. The second bonding metallic layer 1250is formed of at least one of Au, Pd and Pt, preferably of Au.

The aforementioned P-type electrode may be formed in such a manner thatthe contact metallic layer, reflective metallic layer and diffusionbarrier layer are sequentially laminated and heat treated, and the firstand second bonding metallic layers are then laminated or that thecontact metallic layer, reflective metallic layer, diffusion barrierlayer, and first and second bonding metallic layers are sequentiallyformed and then heat treated. Thus, Me (=Ir, Ni, Pt)/Ag/Ru/Ni/Au aresequentially laminated on the P-type semiconductor layer to obtain aP-type electrode having both reflective film property and low contactresistance property.

Hereafter, a method of manufacturing a vertical LED element according tothe second embodiment of the present invention so configured will beexplained.

FIGS. 59 to 66 are a series of sectional views illustrating a process ofmanufacturing the vertical LED element according to the secondembodiment of the present invention.

FIG. 59 is a sectional view of a common GaN LED substrate. On a sapphiresubstrate 1000 are sequentially grown an N-type semiconductor layer1500, an active layer 1400 and a P-type semiconductor layer 1300. Thetotal thickness of thin film is approximately 4 microns. The thin filmis deposited through a MOCVD method.

The substrate 1000 is formed of at least one of Al₂O₃, SiC, ZnO, Si,GaAs, GaP, LiAl₂O₃, BN, A IN and GaN. In this embodiment, a sapphiresubstrate is employed. In this embodiment, a buffer layer that serves asa buffer when forming an N-type semi-conductor layer 1500 may be furtherprovided on the aforementioned substrate. The N-type semiconductor layer1500 preferably employs a GaN film doped with N-type impurities, but notlimited thereto. That is, a variety of material layers having asemi-conductor property may be used. In this embodiment, the N-typesemiconductor layer 1500 is formed to include an N-type Al_(x)Ga_(1-x)Nfilm, where 0≦x≦1. Further, the P-type semiconductor 1300 also employs aGaN film doped with P-type impurities. In this embodiment, the P-typesemiconductor layer 1300 is formed to include a P-type Al_(x)Ga_(1-x)Nfilm, where 0≦x≦1. In addition, an InGaN film may be used as thesemi-conductor layer film. Furthermore, the N-type semiconductor layer1500 and P-type semiconductor layer 1300 may be formed in amulti-layered film. In the above, the N-type dopant is Si, and theP-type dopant is Zn when using InGaAlP or Mg when using nitrides.

The active layer 1400 employs a multi-layered film in which quantum welllayers and barrier layers are repeatedly formed. The barrier layers andquantum well layers may be formed of a binary compound such as GaN, InNand AlN, a ternary compound such as In_(x)Ga_(1-x)N (0≦x≦1) andAl_(x)Ga_(1-x)N (0≦x≦1), or a quaternary compound such asAl_(x)In_(y)Ga_(1-x-y)N (0≦x+y≦1). Of course, the binary to quaternarycompounds may be doped with desired impurities to form the N-type andP-type semiconductor layers 1500 and 1300.

FIG. 60 shows a process of etching an area other than the elementregion. Typically, the etching process is performed through adry-etching method in a state where Cl₂ gas flows after a substrate ismasked using photoresist or SiO₂. The dry etching process is completedand the etching mask is then removed. Thereafter, an insulation film1700 is deposited on the lateral side of the element by depositing theinsulation film 1700 on the whole surface thereof.

Referring to FIG. 61, a portion on which a P-type reflective film ohmicelectrode will be formed is etched and a P-type electrode 1200 is thenformed on. On the substrate etched for the element isolation is formedthe SiO₂ protective film 1700 with a thickness of 0.05˜5.0 micronsthrough a PECVD method. In order to form a reflective film ohmicelectrode 1200, a micro pattern is formed and an etching process is thenperformed using BOE or CF₄ gas through a dry-etching method and using aphotoresist as a mask. Thereafter, a metallic ohmic layer is deposited.

The surface treatment of the P-type semiconductor layer 1300 exposedbefore the ohmic metallic layer is deposited is performed in such amanner that the P-type semi-conductor layer 1300 is immersed in aquaregia solution (HCl:H₂O=3:1) for ten minutes and is then rinsed withdeionized water and dried with nitrogen gas.

Before depositing a metal, the P-type semiconductor layer issurface-treated by immersing it in a solution of HCl and deionized watermixed at a ratio of 1:1 for one minute, and then loaded in an e-beamevaporator in which metallic electrode/Ag/Ru/Ni/Au (Me=Ir, Ni, Pt)layers 1210, 1220, 1230, 1240 and 1250 are sequentially deposited toform an ohmic electrode. Thereafter, the ohmic electrode is heat-treatedusing rapid thermal annealing equipment at a temperature of 100˜700° C.for at least ten seconds under oxygen atmosphere or an atmospherecontaining at least 5% oxygen. That is, it preferred that the ohmicelectrode is heat treated at the temperature of 100˜700° C. for 10˜100seconds under an atmosphere containing 5˜100% oxygen. Then, theelectrical property is measured to calculate the contact resistance ofthe ohmic electrode.

Preferably, the contact metallic layer (Me=Ir, Ni, Pt) 1210, Ag layer1220, Ru layer 1230 are sequentially deposited on the P-typesemiconductor layer 1300 and then heat treated under the oxygenatmosphere. At this time, since the diffusion barrier layer 1230, i.e.the Ru layer, has been formed on the reflective metallic layer, i.e. theAg layer 1220, the Ag layer 1220 can be prevented from being diffused oroxidized during the heat treatment. Next, the Ni layer 1240 and Au layer1250 are deposited on the Ru layer 1230 to form the ohmic electrode.

Alternatively, a dense ohmic electrode may be formed by sequentiallyforming the contact metallic layer (Me=Ir, Ni, Pt) 1210, Ag layer 1220,Ru layer 1230, Ni layer 1240 and Au layer 1250 and then heat treatingthe sequentially formed layers under the oxygen atmosphere. Afterforming the ohmic electrode, a desired patterning process may be carriedout to obtain a pattern targeted for the ohmic electrode on the P-typesemiconductor layer 1300. Of course, the ohmic electrode may be formedon an N-type nitride layer.

The insulation film 1700 can be formed only on the lateral sides of theN-type semi-conductor layer 1500 and active layer 1400. Although theinsulation film 1700 is formed on the whole structure and a part of theinsulation film 1700 formed on the P-type semiconductor layer 1300 isthen etched as described above, the present invention is not limitedthereto. That is, a portion of the insulation film 1700 except theinsulation film 1700 formed on the lateral sides of the N-typesemiconductor layer 1500 and active layer 1400 may be removed afterforming a desired mask on the P-type semiconductor layer 1300 to protecta part of the semiconductor layer 1300 and then forming the insulationfilm 1700 on the whole structure.

FIG. 62 shows a process of forming a metallic protective layer 1100 witha thickness of several microns to several tens of microns and radiatinga laser. The metallic protective layer 1100 is formed through anelectroplating method and a vacuum vapor-deposition method such assputtering, e-beam evaporation or thermal evaporation. When a laser isradiated through sapphire, the laser is absorbed in the GaN layer whichin turn is decomposed into a Ga metal and N gas. At this time, themetallic protective layer 1100 serves to prevent the GaN thin film layerwith a thickness of about 4 microns from being destroyed when thesapphire substrate 1000 is removed by means of the laser radiation. Atthis time, a part of the insulation film may be removed together withthe sapphire substrate.

FIG. 63 shows a state where a GaN thin film layer is wrapped around andprotected by the metallic protective layer 1100 after the sapphiresubstrate 1000 has been removed.

Next, as shown in FIG. 64, an anti-reflective layer 1800 is coated onthe N-type semiconductor layer 1500 such that photons generated in theactive layer (i-InGaN) 1400 can be emitted to the outside of thesubstrate. The anti-reflective layer 1800 is formed of SiO₂, Si₃N₄, ITO,IZO or the like which is deposited through the PECVD, sputter, or e-beamevaporation method.

FIG. 65 is a sectional view illustrating a state after portions of theanti-reflective layer 1800 has been etched and an N-type ohmic electrode1600 has been then formed. The N-type ohmic electrode is formed of Ti/Alor Cr/Au, or Ti/Al or Cr/Au on which Cr/Au or Ni/Au is deposited usingan e-beam evaporator.

FIG. 66 is a sectional view showing a state after the chip has beenseparated. At this time, the chip is separated through a dicing or lasercutting technique.

FIGS. 67 to 69 show a series of processes of manufacturing a verticalLED element according to a modified embodiment of the present invention.

The processes of FIGS. 67 to 69 are similar to those of FIGS. 59 to 61.That is, desired GaN layers, i.e. PN junction layers, are formed on thesubstrate 1000. Then, the element is isolated and the insulation film1700 for protecting the isolated element is formed along the steppedportion. A part of the insulation film 1700 is patterned to expose apart of the P-type semiconductor layer 1300. The P-type electrode 1200is formed on the exposed P-type semiconductor layer 1300.

Next, as shown in FIG. 70, a metallic protective film layer 1100 isformed on the whole structure along the stepped portion, and a metallicsupport layer 1900 is then formed on the metallic protective film layer1100 above the P-type semiconductor layer 1300. That is, it is preferredthat the metallic support layer 1900 with a thickness of 10˜50 micronsbe formed on the metallic protective film layer 1100. As shown in FIGS.71 to 74, the lower substrate 1000 is removed and the anti-reflectivelayer 1800 is then formed on the N-type semiconductor layer 1500.Subsequently, a part of the anti-reflective layer 1800 is patterned toexpose a part of the N-type semiconductor layer 1500 to the outside. TheN-type electrode 1600 is formed on the exposed N-type semiconductorlayer 1500. The chip is separated to complete a vertical LED structure.

Hereafter, a process of manufacturing a vertical LED element accordingto the modified embodiment of the present invention will be explainedwith reference to FIGS. 75 to 82 which is a series of sectional viewsillustrating a method of manufacturing the vertical LED of FIGS. 56 to57.

As shown in FIGS. 75 to 76, a plurality of PN-junction semiconductorlayers are formed on the substrate 1000. The SiO₂-based insulation film1700 is formed at a thickness of 0.05˜5.0 microns using the PECVDmethod. Then, a micro pattern in the form of mesh is formed using aphotoresist film. Using the photoresist film as a mask, the SiO₂ film isdry-etched using the BOE or CF₄ gas such that the P-type semi-conductorlayer 1300 can be exposed in a mesh form.

As shown in FIG. 77, the P-type reflective ohmic electrode layer 1200 isdeposited on the exposed P-type semiconductor layer 1300 that has beenexposed by etching the insulation film 1700. The reflective layer 2000is formed on the P-type semiconductor layer 1300 on which the P-typeelectrode 1200 is formed. The P-type ohmic electrode 1200 is formed bydepositing and heat treating an ohmic metal. Typically, Ni and Au aredeposited at a thickness of several tens to several hundreds ofnanometers using an e-beam evaporator. However, since reflectivity isimportant in case of the vertical LED according to this modifiedembodiment, metals including Ni/Ag, Pt/Ag, Ru/Ag, Ir/Ag or the like areused. Then, the rapid thermal annealing is performed for several secondsto several minutes at a temperature of 300 to 600° C. to form theelectrode. Thereafter, Ag or Al-based reflective film is deposited onthe P-type reflective ohmic electrode in a mesh form. The processes ofFIGS. 78 to 82 are the same as those of FIGS. 59 to 74, and thus,detailed descriptions thereof will be omitted herein.

Next, a process of manufacturing a vertical LED element of this modifiedembodiment will be explained with reference to FIGS. 83 to 90. Here,FIGS. 83 to 90 are sectional views illustrating processing steps ofmanufacturing the vertical LED shown in FIG. 64.

The processes of FIGS. 83 to 85 are the same as those of FIGS. 75 to 77.Referring to FIG. 86, a metallic protective film layer 1100 is formedalong the stepped portion of the whole structure as shown in FIG. 78,and a metallic support layer 1900 is then formed on the metallicprotective film layer 1100. As shown in the figure, since the metallicsupport layer 1900 is not formed in a trench area, a subsequent processof separating the elements can be easily performed. The processes ofFIGS. 87 to 90 are the same as those illustrated in FIGS. 59 to 82, andthus, detailed descriptions thereof will be omitted herein.

In the previous embodiments, the metallic protective film layer 1100 isformed in such a way to wrap around the lateral sides and the bottomside of the element. Further, the metallic support layer 1900 is formedbeneath the metallic protective film layer 1100. Thus, damages due todistortion or impact produced when separating the chip can be minimized.

Furthermore, the aforementioned insulation film 1700 employs an oxidethin film, which is formed of at least one of SiO₂, Si₃N₄, MgO, Al₂O₃,TiO₂, VO₂, ZrO₂, Ce₂O₃, HfO₂, NbO₂, Ta₂O₅, Y₂O₃, V₂O₃ and WO₃. At thistime, the oxide film has a thickness of 100 nm to 100 microns. Inaddition, one or more thin film semiconductors such as GaN, AlGaN, A IN,SiC and diamond having a wide bandgap are alternately laminated to forman insulation film. Such an insulation film has a thickness of 100 nm to100 microns.

The metallic protective film layer 1100 and the metallic support layer1900 are formed of at least one of Au, Ni, W, Mo, Cu, Al, Ta, Ag, Pt andCr. The metallic support layer 1900 has a thickness of 0.5˜200 nm. Inaddition, the metallic protective film layer 1100 and the metallicsupport layer 1900 can be formed by performing the vacuum depositionusing a conductive ceramic film such as SrTiO₃ doped with Nb, ZnO dopedwith Al, ITO and IZO or a semiconductor doped with impurities such asB-doped Si, As-doped Si and diamond doped with impurities.

The P-type electrode 1200 is formed of at least one of Ni, Pt, Ru, Ir,Rh, Ta, Mo, Ti, Ag, W, Cu, Cr, Pd, V, Co, Nb, Zr and Al and has athickness of 5˜2000 nm. In a case where the P-type electrode 1200 isformed in a double-layered form, its first layer is formed of at leastone of Ni, Pt, Ru, Ir, Rh, Ta, Mo, Ti, Ag, W, Cu, Cr, Pd, V, Co, Nb, Inand Zr while its second layer is formed of Ag and/or Al. At this time,the first layer has a thickness of 5˜1000 nm, and the second layer has athickness of 10˜1000 nm. The P-type electrode 1200 may be formed in amulti-layered form having two or more layers. The aforementioned P-typeelectrode 1200 is heat treated for 30 seconds to 30 minutes at atemperature of 300˜600° C. under a nitrogen, oxygen or air atmosphere.In addition, before forming the P-type electrode 1200, a reflectivelayer 2000 is formed on the P-type semiconductor layers 1300 andportions where the P-type electrode 1200 will be formed are thenpartially etched.

Further, the reflective layer 2000 is formed of Ag and/or Al.Alternatively, the reflective layer may be formed of an alloy containingAg and less than 10% of other metals or an alloy containing Al and lessthan 10% of other metals.

Furthermore, the anti-reflective layer 1800 is formed of at least one ofITO, ZnO, SiO₂, Si₃N₄ and IZO and has a thickness of 10˜5000 nm.

INDUSTRIAL APPLICABILITY

As described above, since a double-layered metallic support layer isused as a metallic support layer at the bottom thereof in the verticalGaN LED of the present invention, the chip can be easily separated.

Further, since a thick metallic protective film layer with a thicknessof at least 10 microns is formed on the lateral and bottom sides of theelement, the element can be protected against external impact.

Furthermore, since a P-type reflective electrode is partially formed ona p-GaN layer in a mesh form and a reflective layer is insertedtherebetween, photons generated in an active layer can be maximallyemitted toward an n-GaN layer.

In addition, since a metallic substrate, conductive layer substrate orconductive ceramic substrate is used instead of a sapphire substrate toefficiently release the generated heat to the outside when the elementis operated, it is suitable for a high-power application. Moreover,since photons generated in an InGaN layer are emitted through an n-GaNlayer, a path where the photons are emitted is short. Therefore, thenumber of photons absorbed during their emission can be reduced.Furthermore, since a high concentration of doping (>10¹⁹/cm³) into ann-GaN layer can be obtained, electrical conductivity and thus currentdiffusion resistance can be improved. Therefore, optical outputcharacteristics can be enhanced.

Also, the present invention provides a technique for separating a GaNthin film layer of the LED structure from the sapphire substrate using alaser and a process of manufacturing a vertical GaN LED on the separatedthin film layer.

From the foregoing, it will be understood by those skilled in the artthat various changes and modifications can be made within the technicalspirit and scope of the present invention. Therefore, the spirit andscope of the present invention is not limited to the contents describedin the preferred embodiment but to the appended claims.

1. A light emitting element, comprising: a P-type semiconductor layer;an active layer and an N-type semiconductor layer formed on the P-typesemiconductor layer; an N-type electrode formed on the N-typesemiconductor layer; an insulation film formed on at least a lateralside of the N-type semiconductor layer; and a metallic protective layerfor protecting the P-type semiconductor layer and N-type semiconductorlayer.
 2. The light emitting element as claimed in claim 1, wherein themetallic protective layer is formed on lateral sides of the P-type andN-type semiconductor layers and on a bottom side of the P-typesemiconductor layer.
 3. The light emitting element as claimed in claim1, further comprising an insulation layer formed on a part of a bottomside of the P-type semiconductor layer.
 4. The light emitting element asclaimed in claim 3, wherein the insulation layer extends to a lateralside of the active layer.
 5. The light emitting element as claimed inclaim 1, further comprising an anti-reflective layer formed on theN-type semiconductor layer.
 6. The light emitting element as claimed inclaim 1, further comprising a P-type electrode formed beneath the P-typesemiconductor layer.
 7. The light emitting element as claimed in claim6, wherein the P-type electrode includes a contact metallic layer, areflective metallic layer, a diffusion barrier layer and a bondingmetallic layer.